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Abstract

Background Ankylosing Spondylitis (AS) is not only characterized by pathological bone formation leading to ankylosis, but also by bone loss which may lead to vertebral fractures (VFx). TNF-alpha inhibitors (TNFi) have proven to be effective in blocking the inflammation process. A few studies also showed an increase of Bone Mineral Density (BMD) in AS patients treated with TNFi 1–3 but the incidence of VFx after two years of treatment was increased.3–4

Objectives To evaluate the long-term effect of TNFi on BMD and the incidence of VFx in patients with AS.

Methods Consecutive TNFi naive patients diagnosed with AS according to the Modified New York criteria were included. Patients were recruited from the VUmc and the Amsterdam Outpatient clinic Reade and were treated with TNFi for 4 years. BMD at hip and lumbar spine (LS) were measured at baseline, after 2 and 4 years. T-scores were categorized as “normal BMD”, “osteopenia” and “osteoporosis”, based on the WHO osteoporosis criteria.5 The incidence of VFx was determined by two observers using the Genant method.6

Results In total, 70 AS patients with complete datasets (67.1% male) were included. The mean age was 41.6 years and the disease duration (time since diagnosis) was 9.8 years. At baseline 42% of the patients had a decreased BMD of the hip and 34% of the spine, of whom 19 patients (27%) had both a decreased hip BMD as well as a decreased lumbar BMD. The BMD of spine and hip improved after 2 and 4 years of TNFi treatment (Table 1). In 7 patients (10%), 8 VFx were observed both at baseline and after 2 years. After 4 years of TNFi-treatment 11 VFx were observed in 9 patients.

After 4 years, 2 out of 9 patients with ≥1 VFx had a decreased BMD at hip and lumbar spine whereas the other 7 patients had a normal BMD. The majority of VFx was localized in the mid or lower thoracic spine.

, BMD measurement in spine and hip of 70 AS patients treated with TNFi

Conclusions The percentage of relatively young AS patients with a decreased BMD at baseline of the hip and lumbar spine was high (34–41%). After 4 years of TNFi-treatment the BMD of the lumbar spine improved in 8.6% of the patients and of the hip in 7.2% of the patients. At baseline, several vertebral fractures were found and a few additional vertebral fractures were observed after 4 years of treatment.

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